Parabola 2

Parabola

Parabola is obviously given by two of its dots and by
contact dotsdots in them.
Ratio

For a line AC, where dot B ∈AC is defined ratio (ABC) = (B-A)/(C-B).

Construction of a parabola

Let's assume that we have got given dots A, D and
C and t ∈<0,1>. For dots E, B and F then
it is valid : ratio (AED) = ratio (EBF) = ratio (DFC).
Construction of a parabola lies in drawing a dot of parabola B with
parameter r = t /(1-t).